Polymerization activity of a catalyst system can depend on polymerization conditions, such as temperature and pressure.
After achieving steady polymerization conditions, the polymerization activity of the catalyst system may become unsatisfactory. Then, the amount of catalyst fed to the reactor must be increased or its residence time increased.
When the amount of catalyst is increased, the cost per unit of polymer produced also increases. When the residence time is increased, the productivity of the plant decreases. There is a need to increase catalyst activity after use of the catalyst in a polymerization process.
In ethylene polymerization processes that use Ti-based Ziegler-Natta catalysts with aluminum alkyls and hydrogen as molecular weight regulator, there is a need to (a) reduce ethane generated from ethylene hydrogenation and (b) prevent the unproductive consumption of ethylene.